package com.mori.encrypt.spring.boot.core.util;

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * <p> RSA加密解密工具类  </p>
 *
 * @author mori
 * @since 2020/9/29 16:53
 */
public class RsaEncryptUtil {

	/**
	 * 密钥算法类型
	 */
	public static final String KEY_ALGORITHM = "RSA";

	/**
	 * 密钥的默认位长度
	 */
	public static final int DEFAULT_KEY_SIZE = 128;

	public static void main(String[] args) throws Exception {
		//生成公钥和私钥
		Map<Integer, String> keyMap = initKey();
		// 加密字符串
		String message = "1111111111111111111111111111111111111111";
		System.out.println("随机生成的公钥为:" + keyMap.get(0));
		System.out.println("随机生成的私钥为:" + keyMap.get(1));
		long begin = System.currentTimeMillis();
		String messageEn = encrypt(message, keyMap.get(0));
		long end = System.currentTimeMillis();
		System.out.println("加密时间：" + (end - begin) + "ms");
		System.out.println("明文：" + message);
		System.out.println("加密后的字符串为:" + messageEn);
		begin = System.currentTimeMillis();
		String messageDe = decrypt(messageEn, keyMap.get(1));
		end = System.currentTimeMillis();
		System.out.println("解密时间：" + (end - begin) + "ms");
		System.out.println("还原后的字符串为:" + messageDe);
	}

	/**
	 * 随机生成密钥对
	 *
	 * @throws NoSuchAlgorithmException
	 */
	public static Map<Integer, String> initKey() throws NoSuchAlgorithmException {
		// KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
		// 初始化密钥对生成器，密钥大小为96-1024位
		keyPairGen.initialize(1024, new SecureRandom());
		// 生成一个密钥对，保存在keyPair中
		KeyPair keyPair = keyPairGen.generateKeyPair();
		// 得到私钥
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
		// 得到公钥
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
		String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
		// 得到私钥字符串
		String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
		Map<Integer, String> keyMap = new HashMap<>();
		// 将公钥和私钥保存到Map
		// 0表示公钥
		keyMap.put(0, publicKeyString);
		// 1表示私钥
		keyMap.put(1, privateKeyString);
		return keyMap;
	}

	/**
	 * RSA公钥加密
	 *
	 * @param str       加密字符串
	 * @param publicKey 公钥
	 * @return 密文
	 * @throws Exception 加密过程中的异常信息
	 */
	public static String encrypt(String str, String publicKey) throws Exception {
		//base64编码的公钥
		byte[] decoded = Base64.decodeBase64(publicKey);
		RSAPublicKey pubKey =
				(RSAPublicKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePublic(new X509EncodedKeySpec(decoded));
		//RSA加密
		Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, pubKey);
		return Base64.encodeBase64String(cipher.doFinal(str.getBytes(StandardCharsets.UTF_8)));
	}

	/**
	 * RSA私钥解密
	 *
	 * @param str        加密字符串
	 * @param privateKey 私钥
	 * @return 明文
	 * @throws Exception 解密过程中的异常信息
	 */
	public static String decrypt(String str, String privateKey) throws Exception {
		//64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes(StandardCharsets.UTF_8));
		//base64编码的私钥
		byte[] decoded = Base64.decodeBase64(privateKey);
		RSAPrivateKey priKey =
				(RSAPrivateKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(decoded));
		//RSA解密
		Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		return new String(cipher.doFinal(inputByte));
	}
}
